1. Field of Invention
The inventive subject matter relates a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for detecting pan-serotype dengue virus.
2. Background Art
Dengue virus, the causative agent of dengue fever (DF) and dengue hemorrhagic fever (DHF), is a virus of the genus Flavivirus, a single-stranded enveloped RNA virus with positive polarity. Its RNA encodes approximately 3,400 amino acids. The virus exists as four antigenically-distinguishable serotypes.
Dengue fever is the most common human arbovirus infection worldwide and a serious public health concern accounting for estimates of 100 million infections annually (WHO, Dengue Hemorrhagic Fever: Diagnosis, Treatment and Control. Geneva: WHO (1986); Monath and Heinz, Flaviviruses. In Fields Virology. B. N. Fields, D. M. Knipe and P. M. Howley, (eds.) Lippincott-Raven, Philadelphia. 961-1034 (1996); Thomas, et al, Adv. Virus Res. 61: 235-289 (2003). DF and DHF are found in most tropical areas including Africa, Asia, the Pacific, Australia, and the Americas.
Although the virus is capable of growing in a variety of species of mosquitoes, including Aedes albopictus, Aedes polynesiensis and Aedes scutellaris, Aedes aegypti is the most efficient mosquito vector because of its domestic habitat (Gubler, D. I., Dengue. In The Arboviruses: Epidemiology and Ecology. T. P. Monath (ed.), CRC Press (Boca Raton), p 223-260 (1988)). Four antigenically distinct serotypes of dengue virus have been identified with all causing human diseases (Gubler, et al., Am. J. Trop. Med. Hyg. 28:1045-1052 (1979); Henchal and Putnak, Clin. Microbiol. Rev. 3: 376-396 (1990)). Each of the four serotypes, although distinct, is similar enough to the others to elicit only partial cross-protection following infection (WHO, Dengue Hemorrhagic Fever: Diagnosis, Treatment and Control. Geneva: WHO (1986); Monath and Heinz, Flaviviruses. In Fields Virology. B. N. Fields, D. M. Knipe and P. M. Howley, (eds.) Lippincott-Raven, Philadelphia. 961-1034 (1996)). Following infection, viremia is typically detected early at the onset of symptoms (Halstead, S. B., Epidemiology of dengue and dengue hemorrhagic fever. In Dengue and Dengue Hemorrhagic Fever. D. J. Gubler and G. Kuno, editors. Cab international, London. 23-44 (1997)). Although many dengue infections are mild, some infections result in DHF and dengue shock syndrome (DSS), which are potentially fatal. This usually occurs in a small number of people during a second infection caused by a dengue virus that is different from the virus causing the first infection (Halstead, S. B., Epidemiology of dengue and dengue hemorrhagic fever. In Dengue and Dengue Hemorrhagic Fever. D. J. Gubler and G. Kuno, editors. Cab international, London. 23-44 (1997)).
Dengue virus infection occurs following the bite of dengue virus-infected Aedes mosquitoes, which were previously infected by feeding on infected humans. Symptoms of dengue infection include high fever, severe headache, retro-orbital pain, development of a rash, nausea, joint and muscle pain, and usually start within five to six days following the bite of an infected mosquito. Symptoms of DHF also include marked sub-dermal bleeding, causing a purplish bruise, as well as bleeding from the nose, gums, and gastrointestinal (GI) tract. The fatality rate associated with DHF is at 6 to 30% with most deaths occurring in infants. The management of DHF is symptomatic and supportive, and is aimed at replacement of fluid loss.
It is not possible to make an accurate diagnosis of mild or classic DF based on clinical features alone since many symptoms of DF resemble those of other diseases, such as Chikungunya infection (Nimmannitya, S., Dengue and dengue haemorrhagic fever. In Manson's Tropical Diseases. G. C. Cook (eds.) W.B. Saunders Company, Ltd (London). 721-729 (1996)), measles, influenza, and Rickettsial infections. Differential diagnosis must include malaria and other viral, bacterial, and Rickettsial diseases. Diagnostic methods for infection are typically based on detection of virus, viral antigens, genomic sequences, and detection of dengue-specific antibodies (Shu and Huang, Clin. Diagn. Lab. Immunol., 11: 642-650 (2004)). DHF can, in some cases, be more accurately diagnosed based on clinical signs and symptoms, including high continuous fever for 2 to 7 days, hepatomegaly, hemoconcentration, shock and thromocytopenia.